Folding containers are conventionally known which are composed of long side walls connected, via hinge members, to respective opposite long side portions of a bottom portion formed so as to have a rectangular planar shape and short side walls also connected, via hinge members, to respective opposite short side portions of the bottom portion. The long side walls and the short side walls are set up perpendicularly to the bottom portion to assemble the side walls and the bottom portion into a box form. Furthermore, when the folding container is folded, the long side walls and the short side walls are folded so as to lie on top of the bottom portion. With the folding container assembled in the box form, the long side walls and the short side walls are locked by lock members so as to prevent the long side walls or the short side walls from falling down toward the bottom portion.
By way of example, U.S. Pat. No. 6,290,081 (the embodiment shown in FIGS. 9 to 13) discloses a lock member disposed on each short side wall and composed of one operation portion that is movable along the wall surface of the short side wall, paired lock bars that are movable in the horizontal direction, and a vertical-movement-to-horizontal-movement converting mechanism composed of an inclined cam groove formed in the lock bar and a driven pin projected from the operation portion, the vertical-movement-to-horizontal-movement converting mechanism converting vertical movement of the operation portion into horizontal movement of the lock bars.
When the operation portion is located at a lower position, the tip portion of each of the lock bars is inserted into a fitting recess portion formed in each long side wall to lock the short side wall on the long side wall so as to prevent the short side wall from falling down toward a bottom portion. Furthermore, when the operation portion located at the lower position is moved upward along the wall surface of the short side wall, the paired lock bars are moved horizontally in the direction in which the lock bars approach each other to remove the tip portion of each of the lock bars from the fitting recess portion formed in the long side wall. This cancels the lock state established between the short side wall and the long side wall via the lock member. Thus, the short side wall can be brought down so as to lie on top of the bottom portion.
According to the above-described conventional folding container, when the folding container in an assembled box form is folded, an operator moves the operation portion upward. However, depending on the position of the operator's hand with respect to the operation portion, the operation portion may be tilted instead of remaining lying horizontally, during the upward movement. If the operation portion is tilted during the upward movement, the paired lock bars coupled to the operation portion via the vertical-movement-to-horizontal-movement converting mechanism are inhibited from being smoothly moved in the horizontal direction. This may disadvantageously result in the unreliable cancellation of the lock state established between the long side wall and the short side wall via the vertical-movement-to-horizontal-movement converting mechanism.
Furthermore, a handheld through-hole into which the operator inserts the operator's hand to carry the folding container in an assembled box form is located close to an operation portion operating recess portion into which the operator inserts the operator's hand to move the operation portion of the lock member upward. Thus, in carrying the folding container in the assembled box form, the operator may accidentally insert the operator's hand into the operation portion operating recess portion to move the operation portion upward. As a result, the lock state between the short side wall and the long side wall may disadvantageously be cancelled.
Moreover, when the folding container is in the assembled box form, the operation portion, a leaf spring forming the operation portion, and the vertical-movement-to-horizontal-movement converting mechanism are arranged in the operation portion operating recess portion that is open to the exterior of the short side wall. Thus, an external member may accidentally enter the operation portion operating recess portion. This may disadvantageously damage the operation portion, the leaf spring forming the operation portion, or the vertical-movement-to-horizontal-movement converting mechanism.